From Fig.3a, it is seen that twisted tape of twist ratio 3 enhanced heat transfer more than that with twist ratio 5.This is because twisted tape of twist ratio 3 have severe twist and increase the effect of swirl flow and mixing. Thevalue of Nusselt number obtained in heat exchanger with twisted tape insert of twist ratio 3 and 5 are around 1.5 and1.4 times that of the ordinary heat exchanger. From Fig.3b, it is observed that by the insertion of twisted tape, highertube blockage is experienced and it increases further with decreasing twist ratios. The tube side friction factor ofheat exchanger with twisted tapes of twist ratio 3 and 5 were almost 3.5 and 2.7 times compared to that of ordinaryheat exchanger tube.ations